High-ranking officials of Lukoil, the privately-owned Russian oil giant, were the passengers of the flight. All five of them were killed in the crash, as well as the flight engineer. The second pilot is in critical condition.

Gazpromavia’s Mi-8 helicopter on a Volgograd-Kotovo flight crashed in the Volgograd region at around 10:00 am on Wednesday, a spokesman for Lukoil said. The causes of the crash are being investigated.

“At the altitude of 100 meters the helicopter started shaking heavily, after which it started descending to the lowest possible height,” the surviving flight commander told Interfax.

“When the helicopter started hovering, a loud popping sound was heard at the machine’s tail. When it crashed, the fuel tank caught fire.”